Many location-based services today such as emergency service, mobile yellow pages, and navigation assistance require knowledge of the location of a mobile station prior to providing service and/or information to the mobile station. Typically, the location-based services may query for the location information of the mobile station from a base station subsystem (BSS) or a radio access network (RAN), which in turn, may directly determine the location information from the mobile station via an uplink (i.e., from the mobile station to a base station) amplitude difference-based angle of arrival estimation (AD-AOA). In particular, the base station may take signal strength measurements on at least two directional antennas to determine the bearing (i.e., AOA) from the base station to the mobile station. The difference in signal strength may represent the difference in horizontal pattern gain between the two directional antennas. By comparing the two horizontal patterns, an AOA may be obtained. Because the base station (and/or the base station controller) performs the signal measurements and determines the location of the mobile station (i.e., latitude/longitude or x, y), the mobile station may not provide its location autonomously.
One aspect of designing a wireless communication system is to optimize resources available to the wireless communication system. In particular, one method of improving the availability of resources is to reduce the number of messages exchanged between a location service provider, a mobile station, and the BSS or the RAN. However, as noted above, the mobile station is dependent on the BSS to determine its location. Therefore, a need exists for a mobile station to determine autonomously its angle of arrival (AOA).